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LibGfx: Handle filling complex shapes better

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This allows the painter to render filled complex shapes better, by
constructing a path graph for (interesting) intersecting lines and
omitting lines from the containing segments if they are detected
to take no part in defining the edges of a shape.

This approach would still fail if there are multiple logical shapes
that are confined to the collection of lines.
For instance, two polygons intersecting each other in a way that one
vertex of polygon A ends up inside polygon B.
we would detect that polygon A's edges are part of the shape
(technically correct) even though they are not a part of polygon B at
all.
This commit is contained in:
AnotherTest 2020-05-08 10:03:01 +04:30 • committed by Andreas Kling
parent 14ee090f25
commit 677568e3d4
3 changed files with 201 additions and 13 deletions
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49
Libraries/LibGfx/Path.h
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@ -26,6 +26,8 @@
#pragma once
#include <AK/HashMap.h>
#include <AK/Optional.h>
#include <AK/Vector.h>
#include <LibGfx/FloatPoint.h>
#include <LibGfx/Forward.h>
@ -68,7 +70,22 @@ public:
void close();
struct LineSegment {
Point from, to;
float inverse_slope;
float x_of_minimum_y;
float maximum_y;
float minimum_y;
float x;
};
enum ShapeKind {
Simple,
Complex,
};
const Vector<Segment>& segments() const { return m_segments; }
Vector<LineSegment> split_lines(ShapeKind);
const auto& split_lines()
{
if (m_split_lines.has_value())
@ -80,22 +97,34 @@ public:
String to_string() const;
struct LineSegment {
Point from, to;
float inverse_slope;
float x_of_minimum_y;
float maximum_y;
float minimum_y;
float x;
};
private:
void invalidate_split_lines() { m_split_lines.clear(); }
void invalidate_split_lines()
{
m_split_lines.clear();
m_graph_node_map.clear();
}
void segmentize_path();
void generate_path_graph();
bool is_part_of_closed_polygon(const Point& p0, const Point& p1);
static unsigned hash_line(const Point& from, const Point& to);
Vector<Segment> m_segments;
Optional<Vector<LineSegment>> m_split_lines {};
struct PathGraphNode {
PathGraphNode(u32 hash, const LineSegment& line)
: hash(hash)
, line(line)
{
}
Vector<const PathGraphNode*> children;
u32 hash;
LineSegment line;
};
Optional<HashMap<u32, OwnPtr<PathGraphNode>>> m_graph_node_map;
};
inline const LogStream& operator<<(const LogStream& stream, const Path& path)